Keep Your Heart With All Vigilance
by Nyxelestia
Summary: The most efficient way to keep Roy from killing Lust again is to make it someone who he can't burn; neutering the nosy investigator was just a nice bonus. But Father severely underestimated humans - including the one now sharing his body with Lust. "He slammed the Flame Alchemist against the wall. Inside Lust's head, Maes Hughes cried out in time with Roy Mustang's pained grunt."
1. Chapter 1

_"Keep your heart with all vigilance, for from it flow the springs of life."_

_**Proverbs 4:23**_

* * *

It didn't matter how long Roy stared at the empty hospital bed, Hughes didn't reappear in it. The regulation blanket draped over his lap doing little to warm him in the coma ward's chill. He shivered, wishing he hadn't left his gloves in his own room with Havoc.

But then, if he'd brought his gloves, he might've used them on MP reporting to him now.

"…evidence suggests that he simply…got up and walked away-"

"_Two months!_" Roy snapped, bracing his hands against the arm rests of the wheelchair. He tried to stand up to stare down the MP, but the cauterized claw wounds in his side throbbed at the mere movement forward. Hawkeye gripped his shoulder to keep him seated. He bared his teeth and ground out, "A man doesn't just get up and walk away after two months in a coma, not even one as stubborn as Lt. Col. Hughes!"

The lance-corporal grimaced.

"I'm not attempting to suggest that we believe that's what happened, sir, quite the contrary!" she protested. "I am trying to explain we haven't been able to find any leads so far — what little we _have_ found doesn't make sense!"

Roy opened his mouth his mouth to share exactly what he thought of that explanation.

But before he could, he heard a quiet, "Roy?" from behind him.

He couldn't twist around in his seat without tearing out the stitches, so Lt. Hawkeye started to wheel the chair around for him, even as he tried to turn his head.

"Gracia," he greeted, the wheelchair coming to a pause when he faced her. When her skirt ruffled in time with the fidgeting pair of little legs behind her, he softened his voice and added, "Elicia."

The three-year-old peered out from behind her mother. Recognizing her godfather, she shot across the long-term care ward toward him.

Were it any other day, she would try to greet the half a dozen other unconscious patients in the coma ward on her way to her father's bedside, but today she didn't even notice them.

Were it any other day, Gracia would be calling after her toddler to _walk don't run_ — but today, Gracia was still staring at Maes' empty bed.

Were it any other day, Roy would have been ready to scoop up his honorary niece into his arms. But between the wound itself, the exhaustion of the Lab 3 fight against the homunculus, and the shock of finding out Hughes was missing, he barely managed to wrap his arms around himself to shield his midsection from Elicia as she clambered onto his lap.

"Uncle Roy?" she asked, looking at his hospital patient shirt — the very one her father had been clad in for the last two months. She moved where Hawkeye nudged her. Clutching a lopsided origami flower in her tiny fist, she sat on the leg opposite from his bandaged wound. "What happened to you? Where's Daddy?"

"We're still trying to figure that out, Princess," he said. He looked over the top of her head at the MP and added, "Weren't we, Lance-Corporal?"

The woman looked a step away from quaking in her boots.

Gracia came to the lance-corporal's rescue, following her daughter to stand between Roy's wheelchair and her husband's empty bed.

"That's why I'm here, Roy," she murmured, almost inaudible over the machinery surrounding all the other coma patients' beds. "It's so they see if I might know something…useful."

The silence from the machinery around Hughes' bed unnerved Roy. It reminded him far too much of the silence on the phone two months ago, when his best friend had called him for help — and Roy hadn't picked up in time.

Hawkeye reached over, wrapping a comforting hand over Gracia's shoulder — while her other hand still on Roy's shoulder squeezed tight in warning.

"I need to take the Colonel back to his room," Hawkeye explained, voice gentle and strong. "Why don't we take Elicia with us while you help the investigators?"

"No!" Elicia protested. "Where's Daddy?!"

"They're going to find him," Hawkeye promised, gesturing between Gracia, the nervous lance-corporal, and the two other MPs investigating the empty bed. "We can help them by getting out of their way."

Elicia narrowed her eyes in suspicion, and for a moment she looked so much like her father, Roy couldn't breathe.

Turning to look up at the MP, Elicia asked, "You're going to find my daddy?"

"We're doing everything we can and investigating every lead we find," the lance-corporal promised. She knelt down on one knee to look Elicia in the eye, and Roy grudgingly afforded her some respect for that. "Your father would put us all on parking ticket duty until we retired if we thought of doing anything less."

Elicia thought about it for a moment, then nodded and satisfaction.

"…Okay." She snuggled into Roy's good side, then looked up at Hawkeye and pointed at the handles of Roy's wheelchair. "Let's go to Uncle Roy's room!" she declared, as if it had been her idea all along.

She was very much her father's daughter.

As Hawkeye explained where his and Havoc's room was to Gracia, Roy wrapped his good arm around Elicia and hugged her close. He savored the warmth in his side, and the reassuring weight of her head on his shoulder.

Maes' voice — the one in the back of Roy's head that started up the moment that phone-call went silent and hadn't shut up since — gloated at the comfort Roy drew from the child.

He'd been pestering and nagging Roy about starting his own family for so long. Roy was almost glad the man himself wasn't here to rub his hands in triumph and crow at Roy for drawing so much comfort from a toddler.

Almost.

* * *

Ed had become an emancipated minor the moment he'd become a State Alchemist. The legal bullshit was a pain in the ass, but on the bright side, age minimums no longer applied to him.

That didn't make buying a nice bottle of wine for Mrs. Hughes any easier. He didn't have much drinking experience outside of some beers from Havoc and Breda, and then the bit of brandy Mr. Hughes had given Ed on his sixteenth birthday. He and Al had laughed together when Ed damn near coughed it all back up. But Ed's birthday was also Elicia's, and this had been at their annual joint birthday dinner, so that was the extent of Ed's introduction to booze.

Hughes had promised to teach them a bit more about wine when Ed and Al came back from Dublith — then gotten himself shot the day their train pulled out of Central Station.

As if the coma weren't bad enough, Ed had come back from his nightmare of a trip out to the Xerxian ruins and Risembool, only to find out Hughes had gone missing.

At least the liquor salesman had been helpful, after Ed explained it was a gift for someone else.

The single bottle had cost as much as enough Cretan take out for four adults and a toddler. But didn't regret the dent in his wallet, not when he saw Mrs. Hughes' relief when he showed up on her doorstep.

"You didn't have to bring all this," she tried to say anyway, stepping back to let him into the house.

"It was nothing," Ed promised, setting down the bags on her fancy kitchen counter. "Especially since I'm not bringing good news, exactly. It's…about Ross."

As they pulled down the plates from the cupboards, Mrs. Hughes' strong smile dimmed. "Maes' attacker?"

So she didn't know, then.

"Goddamn bastard," Ed muttered, glaring out toward the living room where Mustang currently sat. He sighed and shook his head. "I'll explain once Elicia's in bed."

Mrs. Hughes' face paled, but she nodded all the same.

Dinner remained a light-hearted affair.

Al helped Elicia with her food as the rest of them ate theirs. Elicia might not have noticed Ed glaring at Mustang, but everyone else sure did. Winry and Mrs. Hughes ignored Ed in turn, keeping to small talk with Mustang.

At least they didn't have to get along to listen to Elicia spill all the juicy drama from her preschool class — and her own occasional hand in it.

Not even four years old and she was already turning into a meddling gossip. Mr. Hughes was going to be so proud when he heard about this.

And that was a 'when', not an 'if'.

After a light dessert, Elicia bid good-night to her Uncle Roy, her Big Sister Winry, and Little Big Brother Ed. Mrs. Hughes didn't even try to be subtle when she told Ed to take care of the dishes, and Roy the table. While she and Alphonse put Elicia to bed, Winry stayed downstairs to enforce the soldiers' separation.

Mrs. Hughes wasn't subtle, but neither was Ed, which was why he'd uncorked the wine and held it out to her when they came back.

"You're gonna want some fortifying for this," was the only explanation he could offer.

Ed wanted a bit of fortifying, too. But he needed to keep a clear hear tonight.

Besides, it was bad enough he was taking after his father in alchemy — no need to add alcoholism on top of that.

So he only set out three glasses on the dinner table, as they all reclaimed their seats. Mustang glared, but still poured out a generous glass for Mrs. Hughes, with much smaller amounts for Winry and himself.

Mrs. Hughes drained half of her glass before she asked, "So what's all this about Ross?"

Ed returned Mustang's glare with a nasty smile, sharper and sweeter than the Cretan baklava they'd just had for dessert. "You wanna tell them the truth, or should I?"

"I am trying to keep them safe!" Mustang snapped.

"Fat lot of good that's doing them, with Hughes missing," Ed pointed out. He turned back to the other three. Ed hadn't even started explaining, but Winry looking a step away from making use of the Rockbells' legendary livers. "Ross wasn't Hughes' attacker, and that wasn't Ross that Mustang immolated a few weeks ago. That was about a hundred and forty pounds of pork transmuted into a human shape." He snapped his thumb out at Mustang. "He worked with Prince Ling's people to smuggle the lieutenant out to the ruins of Xerxes. They're gonna take her to Xing."

Mustang buried his face in his freshly-scarred hand. Mrs. Hughes blinked at them, then drained her entire wine glass. Al's jaw dropped so hard, Ed was amazed it didn't actually fall off. Winry — without looking — reached over to press Al's mouthpiece shut, as Mrs. Hughes poured herself another glass.

As she drained that one, too, Mustang looked up from his pale palms to face her. "Gracia," he started.

But she cut him off, hold up a sharp finger typical of mothers far sterner than herself. She kept that finger up as she, with her free hand, poured herself a third glass of wine.

Mustang winced, rubbing at the scabs shaped like the transmutation circle from his gloves. Ed was looking forward to hearing how the hell Mustang managed to need that, but not tonight.

This time, at least, Mrs. Hughes only drank half the glass. Then she clutched the glass stem with both hands, like a lifeline, as she looked between Ed and Mustang.

"Tell us everything," she demanded.

With one final glare at Ed, Mustang started talking.

* * *

Lust had never actually had a man's body before, but had adapted nonetheless.

So much easier to dress up, at least.

He smirked into the large mirror stationed by the front door. Roy Mustang's vanity was so convenient-

_"He isn't vain!"_

-which almost made up for this annoying new voice in Lust's head.

Almost.

_"Then why the body-length mirror in his living room?"_ Lust challenged — without opening his mouth. Remembering to talk without talking _out loud_ was already tedious.

Especially given his new co-person's tendency to ramble and rave at the drop of a hat.

_"He's the second-youngest State Alchemist and the youngest colonel in Amestris!"_ the idiot snapped. _"He has to manipulate to stay alive, and monitor his appearance to do that, and-"_ The obnoxious voice cut off, but before Lust could be relieved, it added, _"Wait, why am I telling you this?"_

"Believe me, I'd like to know, too," Lust muttered under his breath. Not that it mattered — sharing his new body with its native soul meant they both heard everything.

It was one thing to have a core made up of thousands of displaced souls. A Philosopher's Stone was little more than a metaphysical amalgam, rather than a container for all the individuals.

But this new body's intrinsic soul was a different matter altogether.

_"I have to entertain myself _somehow_ until I figure out how to get out of here and kill you!"_

Lust chuckled, a dark and deliberate sound.

His new metaphysical roommate was annoying, but at least he wasn't _boring_.

Lust started to slant his shoulders, remembered that this new body wasn't a woman, and squared them instead. Perfect. He'd picked out this shirt specifically because of how well his new shoulders filled it. The black silk hugged his chest close enough to show off his fit frame, but not tight enough to scandalize.

Scandal had helped in his old body, but would only hinder in this one.

His new ass was a little smaller, but a fair bit tighter and more muscular, too. The dark denim was so kind to his new behind.

_"Are you ogling yourself?"_

"No," Lust said — out loud, taking a look at his his lips rounded around the word. His short beard — closer to stubble than an actual beard — complimented his jawline. "I'm just…how did you put it?" He tilted his chin up. The solitary light from the streetlamps outside shrouded his face in seductive shadow. "'Monitoring my appearance.'"

The resultant discontented snarling was more of a feeling than a vocalization. Lust could handle feelings, those were easy to ignore.

Attention back on his appearance, he straightened out his belt. Having such slim hips was going to take some getting used to, but at least the crimson-embroidered black leather belt flattered them.

Well-trimmed beard, broad shoulders tapering firm muscles down to a narrow waist, strong legs for days…he'd have no problem twisting anyone he wanted around his little finger.

Especially Roy Mustang.

The incoherent snarling grew into nonverbal rage. Lust smirked as he tilted straightened his head again, street-lamp glinting off the edge of his sharp glasses.

Father's procedure hadn't actually fixed his eyes. He couldn't believe how poorly some humans saw without pieces of fragile glass in front of the most vulnerable part of their bodies! But at least they flattered this new face, balancing the light beard and sharp jaw.

They heard the sound of a car approaching down the street outside — a familiar sound, one which left Lust's new body-mate shivering in fear and determination.

Look who's coming home.

Intimidation was in the presentation — and with Mustang's injuries being what they were, Lust could afford to have a little fun with it. So as the sound of Mustang clambering out of his car drifted in from the cramped driveway, Lust sauntered over to the plush, leather recliner sitting pride of place in the living room.

Leaning into the comfort, Lust brushed his bare fingertips down his collarbone. He undid the top two buttons of his shirt, enough to reveal the tattoo nestled between his pecs, without framing the vibrant red ink on his pale skin.

He breathed in silence as the front door opened. The figure cut a rather un-imposing silhouette in the relative privacy of his own home. The loose-hanging suit and glimpse of bandages left Lust's other self confused and worried — on top of the horrified rage directed at Lust.

Oh, how sweet.

Mustang's flinch when he noticed someone in his living room was so gratifying — but not as much as the confused on his relief on his face.

"Hughes!" he cried out, shutting the door behind him as he walked in. "You're awake! Where were…you…"

"Hey, Roy," Lust crooned, right as Mustang's gaze caught the Ouroboros on Lust's chest.

The other man acted fast.

Mustang's hand shot towards his pockets, but Lust snapped up faster than the colonel could reach his gloves, his fingers all elongated to trap those powerful hands helplessly in a cage of his claws.

He slammed the Flame Alchemist against the wall. Inside Lust's head, Maes Hughes cried out in time with Roy Mustang's pained grunt.

Lust stepped forward as he shrank his talons, keeping Mustang's hands imprisoned against the wall as he approached.

Glaring at Lust, Mustang ground out, "You're not Hughes."

"Not anymore," Lust purred. Mustang's struggling slowed as he recognized these claws, and Lust grinned at the look on Mustang's face as the implication started to sink in.

The last sharpened fingertip disappeared until it was just Lust's bare hands — _Hughes'_ bare hands — gripping Mustang's. Lust pressed their chests together, his lips right by Mustang's ear in a vicious parody of intimacy. "Not since you burned me alive under Lab 3."

He squeezed the hands that had tortured and murdered him, and Mustang writhed against him as the pain shot down those shapely arms.

This was going to be _fun_.


	2. Chapter 2

Maes wasn't sure which part was worse: that he could feel his body pinning Roy's — or that he could feel Lust's enjoyment of it.

He wasn't even sure how he was feeling it. How could he simultaneously be in his own body, and be knee-deep in this swamp of agonized faces in his head? Not just agonized faces, but souls, but don't think about it _don't think about that don't think-_

Some of those faces were tiny — were children's faces.

All of them were dwarfed by the giant, spidery shadow that crawled around Maes in this metaphysical amalgam.

Despite being here, he was also there: in a way, he felt paralyzed, because whenever he tried to move his body, he couldn't…

…and yet he still felt everything Lust did with him. Every motion Lust made, every sensation Lust experienced, Maes felt it all.

He- no, not him. His body, under this demonic being's control, squeezed Roy's hands, the bandages wrapped around those palms getting tangled in Lust's clawed fingertips.

Their chests pressed so close together, Maes could feel Roy's heart beat against his own.

It was almost as horrifying as the look in Roy's eyes, watching what looked like his best friend pin him to the wall.

"What are you?" Roy demanded, a hardness to his voice that Maes hadn't heard since Ishval. "What have you done with Hughes?"

_No, Roy!_ Maes tried and failed to shout. The giant, shadowy spider that stalked around Maes in his head shuddered in silent laughter. _Don't talk to it! Just run!_

Of course, Roy didn't hear him.

The only beings that could hear him were the souls — people! — that were as powerless as Maes, nothing more than whisps of memory and emotion swirling around him.

Maes could feel his lips twisting into a sick smile. Lust used his own muscle memory to hit Roy with Maes' own dazzling grin, the over-the-top one that rarely failed to make Roy grumble like a wet cat, and irritate him right out of his depressive episodes.

"Oh, Mustang-"

Lust stopped, and Maes cursed this insane circumstance again because nary a moment later- "Oh, right. He doesn't call you that — does he, Roy?"

Roy snarled, and Lust squeezed harder. The angry snarl faded into a grimace of pain, Roy's expression getting tighter.

Despite how much he liked to pretend otherwise, Roy was not invincible. It wasn't long before even Roy's desperate attempt at an angry glare vanished behind eyes clenched shut in agony. Roy's heaving chest was warm and hard against Maes' — against Lust's.

He wasn't sure if it was because of Lust, or just his own traitorous body coupled with old memories, but Maes' metaphysical gut clenched tight when he realized he — his body? — was getting hard from Roy's writhing against him.

And Maes wasn't the only one who noticed.

At least Lust's grip on Roy stopped this torture as the demon glanced down, moving his hips experimentally as he tried to parse through the memories Maes couldn't stop from surfacing.

"Huh," Lust said, his chin resting on Roy's shoulder. "You two used to sleep together? I was not expecting that — though in retrospect, I suppose I should have."

While Lust's grip had stopped tightening, it hadn't loosened. Roy struggled to take in a deep breath, two, three, before opening his eyes.

"H-Hughes?" Roy pleaded, voice catching in his desperate search for information. "Are you…in there?"

Lust chuckled, leaning in to press an old, familiar kiss to Roy's neck. Roy's shoulder felt even more familiar, and Maes screamed at the demon.

He aimed another futile punch at the spider shadow in his head, and found himself falling into…into…

Was this what a pool of blood felt like? Little globs of blood that moved of their own accord, rippling into faces before vanishing into the quagmire again.

Maes wondered if they could feel his tears.

"Oh, he is," Lust murmured into Roy's sweaty skin, hot breath ghosting over Roy's ear. "Screaming and being such a nuisance." Lust took a deep breath, the motion pressing their bodies closer together, especially Maes' unwanted hard-on against Roy's hips. "I don't know what for, since this feels pretty good to me. But he is _so_ annoying — I'm tempted to let you burn me again. Maybe if you kill your friend, my next host won't be such a nag."

Was the demon always this insightful, or was this Maes' unwilling influence? Lust could not have phrased the implied threat worse; all the fight in Roy vanished. The man slumped against the wall, breathing ragged like he'd just run a rough raid in the Civil War.

"H-Hughes?" Roy whimpered, leaning his head back to try and look for a man in the eyes of a monster — a human in the eyes of a homunculus.

Of course, Roy didn't find it.

"That's right," Lust said, leaning back enough to flutter his obnoxious eyelashes at Roy. "You try to kill me again, it's your best friend in the whole wide world who takes it." Lust smirked, rolling his hips against Roy's again. "At least, I thought he was just your friend. But I guess you were more?"

Roy, the idiot, twisted his lips into a pained attempt at a smirk right back. "Not since he got married."

"Ugh, _monogamy_ and _fidelity_," Lust grumbled, rolling Maes' eyes. Deep in Maes' head, he flinched with Lust's every derisive word. "Why do humans care so much?"

"Well, I already figured you weren't human," Roy ground out. "But thank you for confirming that for me-"

Lust clenched his hands again, tight enough that Maes feared Lust might break Roy's bones.

Roy threw his head back into the wall his failed attemped to get away from the pain; Maes could feel the _thud_ as much as hear it.

_Stop!_ Maes shrieked. Falling back on his metaphysical heels, the mysterious bog of blood — that somehow didn't soak him in whatever they were made of — rippled around him like a weak whirlpool. _Doesn't your 'father' need him to do some alchemy? He can't do it if you break him!_

In Maes' head, the spidery shadow paused in its prowl.

In the real world, Lust's grip loosened, just a little, just enough for Roy to gasp in a deep, relieved breath.

"You make a good point," Lust muttered. "Unfortunately." At Roy's look of confusion, Lust cheerfully explained, "Not you, Mustang, your friend in here."

_But then,_ Lust continued inside their head. _There are plenty of other ways to hurt a man before breaking him._ The spider was nothing but shadow, yet Maes still got the sensation that it was grinning.

Lust took a step back, but it wasn't for a reprieve; it was leverage. Maes snarled at the spider of shadows in his head, as Lust whirled Roy around, slamming the man face-first into the wall. Roy grunted, twisting his arms in a desperate reach for his gloves, but Lust's inhuman grip didn't budge an inch.

He had Roy's hands crossed over his back, and Maes wanted to throw-up at the unbidden memories of their academy days that floated up to the forefront of his mind, seeing Roy like this again. This had been _their_ stupid, failed experiment, and Lust was already turning a fun memory into another nightmare.

The force of the impact shook loose some miscellany from Roy's pockets, and Lust glanced down out of habit.

The State Alchemist's watch, some shopping receipt, an antibiotic pill bottle, and an origami flower.

A lop-sided, lumpy origami flower, made out of the bright paper that Maes had bought in bulk for his girls a week before he'd been shot, and with childishly imprecise folds.

Maes didn't know why the paper flower, of all things, tipped him over the edge.

Maybe it was the sudden intrusion of the thought of his daughter in the middle of his perversity. Maybe it was this piece of his little angel landing in the homunculus' gaze. Maybe it was realizing his little girl could be in just as much danger as Roy was in now.

He wasn't alone in the discordant rise of his rage and terror and latent love. All around him in this hellscape of his head, he could feel the blood, the faces, the souls wrapping around him and lifting him, Maes rising atop the cresting wave.

Were they feeling what he felt?

Were there parents in there?

Whatever the reason, the homunculus was no match for the tsunami of _loveterrorpleasedon'thurtherDON'TYOUDARE_ the moment their eyes caught sight of Elicia's handiwork.

Maes ripped his own hands away from Roy, careening back as far away from his best friend as he could.

"Roy, _RUN_!" Maes screamed. He collapsed, falling to his fours as Lust grappled for control again.

In the amalgam, that flash of paternal passion dissipated as the spider shadow broke through the wave. It descended upon Maes with a shriek, far too many legs and an overbearing weight wrapping around him.

The last thing Maes managed to do was clench his fists.

When Lust finally regained control, those reactionary claws pierced through his own palms.

Lust's shout of pain was drowned out by the wave of flames that surrounded them.

Surrounded, but didn't touch.

Of course Roy hadn't listened to him.

Looking up from their stabbed hands, Lust glared up at Roy, who finally had both of _his_ hands gloved and flame at his command again.

Maes recognized this ring of white-hot blaze.

If Maes were still human, Roy could've flash incinerated him by controlling the ring.

He did his best not to think beyond that, focusing on the moment lest Lust get wind of any weakness in Maes' head.

Roy's hand was up and ready to snap, but his eyes were narrowed down at Lust — and at Maes.

"So he _is_ in there?" the Flame Alchemist said.

Maes cursed his stupidly loyal best friend with every harsh word he'd ever picked up in the entirety of his military career (and had tried to forget when Elicia was born).

But Roy couldn't hear him, and Lust didn't care.

"I told…you so…" Lust ground out, extracting the claws from their palm. The giant, spidery shadow in Maes head seemed to become an equal mass of tiny ones, crawling over Maes' skin as one of those faces formed in the blood and dissolved _into_ the shadow being.

Lust's palm healed, flesh knitting together and skin smoothing over until, only the blood remained as evidence of Maes' pathetic rebellion.

"You already knew that I'm not as easy to kill as you thought," Lust challenged Roy. "And now you know that burning me won't kill me…only hurt your friend." Tracing the arc of the ring of fire with a bloodied hand, Lust shook their head in exactly the same way Maes did when Elicia was being silly — or Roy was being stupid. "So why don't you put out this empty threat of a fire so we can talk-"

The ring contracted, and both Maes and Lust flinched — Maes from memories of Ishval, and Lust from memories of Lab 3.

The flames didn't burn them, or even singe Lust's nice outfit…but the silk was starting to soak through with sweat.

"So you can skewer me with those claws?" Roy challenged. "No thanks."

"How long do you really think you can hold this?" Lust challenged.

"I don't know," Roy answered, expression saturated in a darkness Maes had once prayed to never see again — yet found himself grateful to see now. "But with my best friend's life on the line? Why don't we find out together."


End file.
